In the case of modern types of wind energy installations with a horizontal rotor axis, alignment with the wind is necessary. This is done by swiveling the nacelle with respect to the fixed tower in the azimuth direction, in order in this way to slave it to the main wind direction. In this case, during operation, various azimuth directions are moved to in a randomly distributed sequence, corresponding to the stochastic wind direction distribution. In the process, the nacelle frequently carries out more than one complete revolution relative to the tower. This places stringent demands on the electrical transmission devices between the tower and the nacelle.
Attempts have been made to use rotary transmitters based on the principle of sliprings (DE 20116756 U1). Although these offer the advantage of a theoretically unlimited rotation capability, this advantage is, however, in practice, cancelled out because the wear is not negligible. Furthermore, at high current levels, such as those which typically occur in the power cables, sliprings are sensitive to dirt and resistance increases produced by it. Overall, they have therefore not been proven suitable for reliable long-term operation.
In order to avoid these disadvantages, the cable itself is used as a transmitter by being guided in a hanging loop from the tower into the nacelle. The loop allows the cable to be twisted well, although without an unlimited rotation capability. In practice, it has been found that it is sufficient to design the nacelle to be able to rotate through two or three revolutions in each direction. If the cable does not become untwisted on its own given operation as the wind rotates back, then it must be specially untwisted, by swiveling the nacelle, when a maximum rotation angle is reached.
The second-mentioned variant with the loop has been widely implemented. However, it has been found that particularly in the case of high-performance wind energy installations having a multiplicity of cables, this results in the difficulty that the individual cables rub against one another as they twist, and are therefore subject to excessive wear. This results in the risk of damage to the cables, which can lead to damage to the wind energy installation, for example as a result of a short circuit.
In order to avoid such damage, it is known for star-shaped spacers to be provided for the cables (WO 00/36724 A2). The cables are clamped thereon and are therefore fixed in their relative position. In order to allow the cable run to twist, a loop is formed, whose upper end is held on the nacelle, and whose other end is held on the tower. Furthermore, intermediate spacers are provided which are each attached to the tower via a guide which can swivel, and guide the cable run such that it can move partially. The guides require a large amount of physical space, and are complex.